Electric motor



Fell 1 1934- T. s. BINDSCHEDLER 1,946,463

ELECTRIC MOTOR Filed Aug. 14 1931 3 Sheets-Sheet l INVENTOR YZeooore 52/70 507; ed/er ATTORNEYS Feb. 13, 1934. T. s. BINDSCHEDLER ELECTRIC MOTOR Filed Aug. 14.

Feb. 13, 1934. T. s. BINDSCHEDLER I 1,946,468

ELECTRIC MOTOR Filed Aug. 14. 1931 3 Sheets-Sheet 3 INVENTOR fizeadoreiBindsche ier ATTORNEYS Patented Feb. 13, 1934 lTED STATE LQdfiAdS ELECTRIC MOTOR Theodore S. Bindschedler, Detroit, Mich, as- I signer to Eurroughs Adding Machine Com parry, Detroit, Mich a corporation of Michigan 7 application August 11 i, with Serial No. 557,051 llil Claims. (63E. na e-re) This invention relates to an electric motor. It is directed particularly to a small universal motor, that is, one that will operate on tooth direct and alternating current.

The motor has been devised especially for driving calculating and bookkeeping machines and it has been illustrated in the drawings as used for such purpose. Calculating machines are designed to operate at definite normal speeds and, unless operated at these speeds, the machines will often not perform satisfactorily. If the starting torque of a motor driving such a machine is small, the machine will he oper ated slowly. On the other hand, if the starting torque is high, the machine will be operated with a hang that will be detrimental to successfill operation and harmful to the machine. in some cases, calculating machines are used only a few times a day and the entries made on them are of small figures requiring the operation oi only apart of the mechanism, whereas, in other offices, the machines are in constant operation almost day and night and theentries may he of large numbers requiring operation of all the mechanism. The electric current supply in different cities, states and countries varies greatly in character, that is, it may be direct or alternating, its voltage may vary and the ire quency, when alternating current is used oiten varies. A motor that drives calculating ma= chines should be capable of giving equal starting torque under all these varying conditions.

The type of motor most suitable for these conditions is a series-wound commutator motor and the invention relates to this type of motor. The difficulty with series-wound commutator motors has been that the torque is usually much greater with direct current than with alternating current. Tins is due largely to the fact that, when the motor is operating with direct cur= rent, the current flow through the armature is opposed only by the resistance of the winding and the counter-electromotive force oi the armature whereas, when the motor is operating with alternating current, the current flow is opposed not only by the resistance of the wind ing and the counter=electromotive force of the armature but also by the self-induction or re actance oi the field and armature. "The latter factor greatly reduces the amount of alternating current that will flow through the armature for a given voltage and, since the torque is a iunction oi the amount oi current flowing, the torque of the motor when used with alternating current is much less than when used with direct current.

The present invention comprehends the pro= duction motor that will have substantially the same starting torque on alternating current as on direct current.

The general object of the invention is to pro= vide an improved universal motor.

A further object is to provide an improved motor construction in which the reactance oi the windings to alternating current is greatly reduced.

Another object is to provide an. extremely simple and inexpensive motor construction.

' Still another object is to provide a motor that will he very small so that it can he placed in a small space on a calculating machine, and one that is very light so that it will not add greatly to the weight of a calculating machine.

Qther objects and advantages oi the invention will appear from the following specification and drawings.

An embodiment oi the invention is shown. in the accompanying drawings in which:

Figure l is a perspective view oi the motor.

Fig. 2 is an end elevation with one oi the end cover plates removed to show the interior construction, the view being taken irorn the com inutator end of the motor.

Fig. 3 is a section on the line 3-3 of f2 huTt with the end cover of the motor in position.

rig. 4 is a view similar to Fig. a but with the windings shown diagrammatically and with some of the parts broken away to show others more clearly.

5 is a slreletoniaed view illustrating dia= grammatically the position oi the lines of li s with the improved i-leld construction.

Fig. 6 is a slzeletcnized view similar to 5:

of a small series-wound commutator ill Oil

showing the paths of the lines of hut; in an old type or construction, this view being for the purpose of comparison.

Fig. 7 is another slreletonizedvlew with the armature in place showing the distribution or the lines of flux through the armature.

Fig. e is a view similar to i with the old style armature construction, this view being for comparison.

The motor is a series-wound commutator mo tor with the armature winding connected in se ries with the field. As previously mentioned, the flow of direct current through such a motor is opposedmainly by the resistance of the field and armature windines and the counter-electro- Mill motive force of the are hand. the flow alternat opposed by the resistance oi the the armature lilut also by the s actancc oi the armature and the starting torque of the :motor mately the same with alternating c rent. l'lne r duce the reactance of 'th induitt'lun oi th held Referring to Figs. 1 and 5, it w ll be obs that the laminations in field are I or sets. motor illustrated, the motor being a tor.

l'i pole "no- These groups will be designated lb, ll. and

12, respectively.

Each group comprises a plurality of arcuate ided w th projecting portions laminations rov 13 and 14 i ng pole pieces around which the field r indings may be wound. Each group of laminations is held tightly together by means oi? bolts or rivets l5 and 16 which pass through the laminations; through end plates is and 17 (Fig. 1); and through annular connecting plates 18 and 19 made of non-magnetic meta1. Each group of laminations is thus held rigidly together and the groups are mechanically united and held in proper relation to each other but each group is magnetically separated from the other, that is, there is no metal to conduct the lines of flux from one group of laminations to the other.

This tends to concentrate the flux in three groups in a six pole motor as illustrated in Fig. 5 which is a reproduction of the actual distribution of the flux without the armature in position as indicated by a demonstration test with iron filings. The distribution without the armature in position has been illustrated for the sake of clearness, the distribution with the aroma-- ture in position being illustrated in Figs. 6 and "I. It will be observed that most of the lines of flux for any one group of laminations, for example, group 10 ,in Fig. 5, pass between the north and south poles of this group with very little leakage to the other groups. This is due largely to the fact that there is no iron return path from groups 11 and 12 to group 10. The

easiest path for the lines of flux is from the.

ent than that obtained with the old type of field construction illustrated in Fig. 8, which reproduces the result of a demonstration test with iron filings of the type oifleld frame illustrated in Fig. 6 without the armature in position. It will be observed that, with the old type, the flux is of laminations, instead of :t iron, is empty. ..l1e end plates 13 made of a light non-magnetic metal aluminum and there are only two of t. tively thin plates. This lightening of the com structlon is an important factor where motors are used on devices that must be frequently moved, such as portable calculating machines.

The field windings 20 are wound around the poles as illustrated diagrammatically in Fig. 4, the windings being connected in series. These windings are preferably 01 the loose skein type illustrated in Fig. 3, as such construction reduces the reactance and helps improve the characteristics of the motor.

The characteristics of the motor are Iurther improved by the armature construction which is employed in combination with the held.

Referring to Fig. 7 it will be noted that the armature laminations 30 are annular in shape and only slightly wider than the armature slots 31. These laminations are embedded in a body of balrelite 32 which is molded onto the armature shaft 33, the shaft having a roughened portion 34 illustrated in Fig. 3, which enables the moulded bakelite to firmly grip the shaft without turning.

The armature laminations are prevented from turning in the bakelite by means of slots or keyways 35 into which the bakelite is moulded at the time the armature is made. The armature is constructed by assembling the annular laminations in a suitable fixture, placing the armature shaft in position, placing powdered bakelite, or the like, in the center opening, and subjecting the whole to heat and pressure which causes the bakelite to become a solid mass. The laminations are held firmly together by the bakelite body which also holds them on the arms.- ture shaft and insulates them from it. The bakelite also forms the support for the ends of the commutator supported by the armature shaft 33, the armature windings being connected in series of the field in the well-known manner.

This armature construction reduces the reactance of the armature to alternating current by reducing the amount of iron in the armature circuit. The reactance is the function of the iron in the circuit so that by reducing the amount of iron in the armature circuit, the reactance of the armature is reduced. This is done without reducing the useful torque-creating flux because the lines of force are concentrated in the annular lamination in which the armature conductors are located and the inner edges of the annulanlarninations are more highly saturated than is the iron in the ordinary construction. In the old style construction, such as shown in Fig. 8, wherein the laminations are disk-shaped instead of annular, and where they are keyed to a steel shaft, the inner portion of the amature and the shaft form an iron path for the flux which is not highly saturated and which increases the amount of iron in'the circuit without increasing the torque. Part of the energy is spent in heating the armature shaft due to the non-laminated characmr of the shaft.

Another important point is that the torque oi the armature is reduced with direct current. With an old style armature having dish laminations connected directly to a steel armature shaft, the inner portions of the disks and the armature shaft form an iron path for the flux which. enables a direct current to create a maximum flux.v With the new construction, the annular laminations become saturated more quickly and there is no additional iron path for the flux. The body-oi insulating material forms no such path and the armature shaft is separated from the laminations by this insulating material so that the flux cannot reach the shaft easily. The tendency is to decrease the flux generated by direct current and thus decrease the torque.

The advantages mentioned contribute to mak ing the torque characteristics of the motor on al ternating and direct current more nearly equal.

'By reducing the reactance to alternating current,

more current flows and the torque is increased. By reducing the flux generated by direct current the direct current torque is decreased with the result that the torques on direct and alternating current approach each other.

Another advantage of the construction is that the armature is lighter and therefore has less inertia. This enables quiclr starting and stopping, Taking into consideration that this result is achieved without reducing the torque, it will be appreciated that much better starting and stop= pin characteristics are obtained.

Another novel feature oi the present motor the manner in which it is combined with a calcu lating machine to drive it. Referring to one of the side plates on of acalculating machine is shovni through which projects the main drive shaft 51 of the machine. Instead oi having a separate motor connected through clutch and reduction gear to the drive shaft of the calculating machine, the armatureoi the motor is mount ed directly on the drive shaft and is supported by it. The drive shaft also supports the commutator to, there being no bearing at the left hand end of the armature as illustrated in Fig. 3.

This. construction is made possible by the light nature end. The field frame is supported independently of the armature by the side frame of the calculating machine. Bolts 51 pass through openings in the circular end plates 18 and 19 of the field frame and into the calculating machine frame plate 50. These bolts are also used to hold an end cap 52 of insulating material, preferably bakelite, which closes the outer end of the motor and supports the brushes 53 for the commutator.

While the construction illustrated is the preferred construction, it is to be understood that it has been shown for purposes of illustration only and that variations may be made in it without departing from the spirit and scope of the invention as defined by the appended claims. The explanation of the causes for the improved characteristics is believed to be correct and is the best that can be given at the present time.

I claim:

1. An electric motor for use on both altermating and direct currents having a field frame comprising individual groups of laminations of magnetically permeable material, said groups forming field poles, windings on said poles, nonmagnetic means supporting said groups of laminations in spaced relation to provide a split and balanced magnetic held, an armature within said field frame having a commutator, and a winding on said armature in series with the windings on said poles.

2. An electric motor for use on both alternating and direct currents having a field frame comprising individual groups of laminations of magnetically permeable material, each group forming two field poles, windings on said poles, non-magnetic means supporting said groups of laminations in spaced relation to form a split and balanced magnetic iield, an. armature having a commutator, and a winding on said armature in series with the windings on said poles.

3. electric motor for use on both alternating and direct currents having a field frame comprising individual groups oi arcuam iaininations of magnetically permeable material, each group forming two pole pieces, windings on said pole pieces, an-

nular rings or non=rnagnetic material supporting said groups of laminations in spaced relation to provide a split and balanced field, an armature within said frame having a commutator, and

a winding on said armature connected to said 1 commutator in series with said field pole and di" ct currents having a field frame comprisindividual groups of laminations of magneti cally permeable material to ining pole pieces, windings on said pole pieces, non-magnetic means o ting said groups oi laminations in spaced n to form a split and balanced field, an armature having an armature and a commutator, said armature also having annular lamina-= tions oi magnetically permeable material-spaced at a substantial distance from said armature shaft, a body of phenolic condensation material between said armature shaft and said annularlarninations i'or rigidly supporting said laminations mechanically on said shaft, for insulating them from said shaft, and for separating them magnetically from said shaft, and a winding on said armature connected in series with said field windings.

5. In a motor adapted to operate on both alterhating and direct currents, an armature com prising a plurality of annular laminations oi mag= netically permeable material, a shait, and a body llll Mill

of insnlati rigidly eoneei .riiidiai "3. Iii. netting IJJ-n ilA i: filly u tions rigidly on "ind shlitt, an o laminations from said shaft netica'ily' separate said ian shaft, said iaminations having oii'ti receive an armature winding 4 has been eompieted.

8. In a motor adapted to on either direct or alternating current, an armature eom prising a shaft, a group of slotted annular .iflIilinations of magnetically permeable materiai surrounding said shaft and spaced a substantial distance therefrom, a body of phenolic condensation material fixed to said shaft and having said laminations embedded in it with portions of said body extending partially over the ends of the group of laminations to hold said laminations rigidly together, said body of phenolic condensation maone .1 at t d o said an 0. salt.

' e i tions extent i; over ends of said group oi laminations to inold them together and extending outwardly on said shaft to form supports for armature wind ngs placed on said laminations after said armature has been completed, and an arma ture winding on said iaminations having its ends supported by the projecting portions of said body of phenolic condensation material.

THEODORE {5. BINDSCHEDLER. 

